Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$179.50	4.461%	$187.5075	$187.51	$187.50	$187.50
Purchase #2	$40.97	8.177%	$44.3201	$44.32	$44.30	$44.30
Purchase #3	$67.64	7.365%	$72.6217	$72.62	$72.60	$72.60
Purchase #4	$151.71	8.734%	$164.9604	$164.96	$164.95	$165.00
Purchase #5	$131.27	13.294%	$148.721	$148.72	$148.70	$148.70
Purchase #6	$108.76	4.232%	$113.3627	$113.36	$113.35	$113.40
Purchase #7	$65.46	7.411%	$70.3112	$70.31	$70.30	$70.30
7 purchase totals =	$745.31		$801.8046	$801.80	$801.70	$801.80